Lactose intolerance (also known as hypolactasia) is a condition that affects approximately 70% of the world's population and symptoms include bloating, flatulence and diarrhoea. It is caused by the inability to digest lactose due to the down regulation of the enzyme lactase. As a result, lactose is not digested by the body and passes into the colon where it is fermented by gut bacteria into fatty acids and various gases, the most notable being hydrogen. Milk contains 4-6 g lactose/100 ml, but because it provides a very rich source of calcium and vitamin C, lactose free milk and milk products are in high demand. These products contain less than 0.25 g lactose/100 ml of milk and are produced by the hydrolysis of lactose into its two monomers, galactose and glucose, by the enzyme lactase (β-galactosidase).
